Method for estimating frequency offset in system utilizing a plurality of sub-carriers

Abstract

An integer frequency offset estimation scheme in an orthogonal frequency division multiplexing (OFDM)-based system is disclosed. A receiving apparatus for receiving a signal according to an OFDM includes an OFDM symbol acquisition module for acquiring at least two consecutive OFDM symbols, a symbol operation module for operating upon pilot symbols and/or data symbols belonging to frequency bands determined according to a plurality of candidates for integer frequency offsets among a plurality of pilot symbols and a plurality of data symbols included in the acquired OFDM symbols, and an integer frequency offset estimation module for selecting a final integer frequency offset among a plurality of candidates for integer frequency offsets according to magnitudes of operation values obtained by the symbol operation module, wherein the frequency bands determined according to the candidate for integer frequency offsets are obtained by frequency-shifting preset frequency bands at which all pilot symbols are transmitted according to the candidate for integer frequency offsets.

1. A receiving apparatus for receiving a signal according to an orthogonal frequency division multiplexing (OFDM) scheme, the receiving apparatus comprising:
 an OFDM symbol acquisition module for acquiring at least two consecutive OFDM symbols; 
 a symbol operation module for operating upon pilot symbols and/or data symbols belonging to frequency bands determined according to a plurality of candidates for integer frequency offsets among a plurality of pilot symbols and a plurality of data symbols included in the acquired OFDM symbols; and 
 an integer frequency offset estimation module for selecting a final integer frequency offset among the plurality of candidates for integer frequency offsets according to magnitudes of operation values obtained by the symbol operation module; 
 wherein the frequency bands determined according to the plurality of candidates for integer frequency offsets are obtained by frequency-shifting preset frequency bands at which all pilot symbols are transmitted according to the plurality of candidates for integer frequency offsets; 
 wherein the symbol operation module includes:
 correlation modules equal to a number of the plurality of candidates for integer frequency offsets; and 
 a template module for providing the correlation modules with template information about pilot symbols included in the OFDM symbols; 
 
 wherein each of the correlation modules operates, using the template information, upon pilot symbols and/or data symbols belonging to frequency bands determined according to one candidate integer frequency offset; and 
 wherein the template information is information about a ratio of different pilot symbol values. 
 
     
     
       2. The receiving apparatus of  claim 1 , wherein the OFDM symbol acquisition module includes:
 a Fourier transform module for performing Fourier transform upon a received signal; and 
 a time delay module for acquiring the at least two consecutive OFDM symbols by time-delaying an output of the Fourier transform module. 
 
     
     
       3. The receiving apparatus of  claim 1 , wherein each correlation module calculates multiplications of all combinations of pilot symbols and/or data symbols belonging to frequency bands determined according to the one candidate for integer frequency offset, operates upon the calculated multiplications according to the template information, and sums operation values according to the template information. 
     
     
       4. The receiving apparatus of  claim 1 , wherein the pilot symbols are continual pilot symbols or scattered pilot symbols. 
     
     
       5. A method for estimating an integer frequency offset, wherein the method being performed by a receiving apparatus for receiving a signal according to an orthogonal frequency divisional multiplexing (OFDM) scheme, the method comprising:
 at an OFDM symbol acquisition module included in the receiving apparatus, acquiring at least two consecutive OFDM symbols; 
 at a symbol operation module included in the receiving apparatus, operating upon pilot symbols and/or data symbols belonging to frequency bands determined according to a plurality of candidates for integer frequency offsets among a plurality of pilot symbols and a plurality of data symbols included in the acquired OFDM symbols; and 
 at an integer frequency offset estimation module included in the receiving apparatus, determining a final integer frequency offset among the plurality of candidates for integer frequency offsets according to magnitudes of operation values obtained by the operating; 
 wherein the frequency bands determined according to the plurality of candidates for integer frequency offsets are obtained by frequency-shifting preset frequency bands at which all pilot symbols are transmitted according to the plurality of candidates for integer frequency offsets; 
 wherein the operating upon the pilot symbols and/or data symbols includes:
 at a symbol operation module included in the receiving apparatus, acquiring template information about pilot symbols included in the acquired OFDM symbols; and 
 at a symbol operation module included in the receiving apparatus, calculating a plurality of operation values corresponding to the plurality of candidates for integer frequency offsets, by operating, using the template information, upon pilot symbols and/or data symbols belonging to frequency bands determined according to the plurality of candidates for integer frequency offsets among a plurality of pilot symbols and a plurality of data symbols included in the OFDM symbols; and 
 
 wherein the template information is information about a ratio of different pilot symbol values. 
 
     
     
       6. The method of  claim 5 , wherein the acquiring at least two consecutive OFDM symbols includes:
 performing Fourier transform upon a received signal; and 
 acquiring the at least two consecutive OFDM symbols by time-delaying the Fourier transformed output. 
 
     
     
       7. A receiving apparatus for receiving a signal according to an orthogonal frequency division multiplexing (OFDM) scheme, the receiving apparatus comprising:
 an OFDM symbol acquisition module for acquiring at least two consecutive OFDM symbols; 
 a symbol operation module for operating upon pilot symbols and/or data symbols belonging to frequency bands determined according to a plurality of candidates for integer frequency offsets among a plurality of pilot symbols and a plurality of data symbols included in the acquired OFDM symbols; and 
 an integer frequency offset estimation module for determining a final integer frequency offset among the plurality of candidates for integer frequency offsets according to magnitudes of operation values obtained by the symbol operation module; 
 wherein the symbol operation module includes:
 a grouping module for performing grouping; 
 correlation modules of a number equal to a number of the plurality of candidates for integer frequency offsets; and 
 a template module for providing the correlation modules with template information about pilot symbols included in the OFDM symbols; 
 
 wherein each of the correlation module operates, using the template information, upon pilot symbols and/or data symbols belonging to frequency bands determined according to one candidate for integer frequency offset by individually operating upon pilot symbols and/or data symbols contained in each of the frequency band groups, and sums intermediate results calculated individually from each frequency band group, thereby generating an operation value; and 
 wherein the template information is information about a ratio of different pilot symbol values. 
 
     
     
       8. The receiving apparatus of  claim 7 , wherein the OFDM symbol acquisition module includes:
 a Fourier transform module for performing Fourier transform upon a received signal; and 
 a time delay module for acquiring the at least two consecutive OFDM symbols by time-delaying an output of the Fourier transform module. 
 
     
     
       9. The receiving apparatus of  claim 7 , wherein the correlation module calculates multiplications of all combinations of pilot symbols and/or data symbols belonging to each of the frequency band groups, operates upon the calculated multiplications according the template information, and sums operation values according to the template information. 
     
     
       10. The receiving apparatus of  claim 7 , wherein the pilot symbols are continual pilot symbols or scattered pilot symbols. 
     
     
       11. A method for estimating an integer frequency offset, wherein the method being performed by a receiving apparatus for receiving a signal according to an orthogonal frequency division multiplexing (OFDM) scheme, the method comprising:
 at an OFDM symbol acquisition module included in the receiving apparatus, acquiring at least two consecutive OFDM symbols; 
 at a symbol operation module included in the receiving apparatus, operating upon pilot symbols and/or data symbols belonging to frequency bands determined according to a plurality of candidates for integer frequency offsets among the plurality of pilot symbols and a plurality of data symbols included in the acquired OFDM symbols; and 
 at an integer frequency offset estimation module included in the receiving apparatus, determining a final integer frequency offset among a plurality of candidates for integer frequency offsets according to magnitudes of operation values obtained by the operation; 
 wherein the operating upon the pilot symbols and/or data symbols includes:
 at a symbol operation module included in the receiving apparatus, acquiring template information about pilot symbols included in the acquired OFDM symbols; and 
 at a symbol operation module included in the receiving apparatus, calculating a plurality of operation values corresponding to the plurality of candidates for integer frequency offsets, by operating, using the template information, upon pilot symbols and/or data symbols belonging to each of the frequency band groups among pilot symbols and/or data symbols belonging to frequency bands determined according to each of the plurality of candidates for integer frequency offsets and summing intermediate results calculated individually from each of the frequency band groups; and 
 
 wherein the template information is information about a ratio of different pilot symbol values. 
 
     
     
       12. The method of  claim 11 , wherein the acquiring at least two consecutive OFDM symbols includes:
 performing Fourier transform upon a received signal; and 
 acquiring the at least two consecutive OFDM symbols by time-delaying the Fourier transformed output.